Method of pepositing materials

ABSTRACT

A coherent material is formed on a substrate ( 10 ) by providing a precursor suspension ( 14 ) in which particulates are suspended in a carrier fluid, and directing the precursor suspension ( 14 ) at the substrate ( 10 ) from a first source ( 12 ). Generally contemporaneously with application of the deposited precursor suspension ( 14 ) to the surface, hot gases, e.g. hot gases produced by a flame ( 16 ), are directed at the substrate ( 10 ) from a remote second source ( 18 ) to fuse the particulates into the coherent material.

[0001] The present invention is directed to deposition of coherentmaterials, such as bodies, films or coatings, most particularly films orcoatings. Oxide coatings formed in accordance with the invention may beused as protective coatings, thermal barriers or electrical insulation.Similar uses may be found for polymer coatings deposited in accordancewith the present invention. Metal coatings formed in accordance with theinvention may be used for electrical conduction, and certain metals maybe applied over corrosion-sensitive substrates to provide corrosionresistance.

BACKGROUND OF THE INVENTION

[0002] U.S. Pat. No. 5,652,021 describes a flame-based depositiontechnique termed combustion chemical vapor deposition or “CCVD”. U.S.Pat. No. 5,997,956 describes a CCVD process using near-supercriticalfluid solutions. The teachings of each of the above-mentioned U.S.Patents are incorporated herein by reference. The techniques taught inthese patents allow for large-scale, open-atmosphere deposition of filmsor coatings of a variety of materials, including metals, polymers, metaloxides, metalloid oxides, and mixed oxides, as thin layers on varioussubstrates and also provide for production of powders of fine, generallyuniform size. In these processes, atomization of chemical precursorsolutions may be effected by passing the precursor solutions underpressure through narrow diameter needles or nozzles.

[0003] While CCVD is an effective means of depositing very thin films,and while thicker films may be deposited by increasing deposition timesand/or increasing the number of passes of a CCVD flame over a substrate,there may be practical constraints that limit the usefulness ofdepositing thicker films or coatings, e.g., 10 microns or greater, byconventional CCVD. Accordingly, it is a primary object of the presentinvention to produce relatively thick coatings, e.g., 10 microns thickor above, preferably 20 microns thick or above. However, the inventionis not limited to these thicknesses, and the invention is generallyuseful for depositing coherent materials, such as films or coatings, asthin as about 0.1 micron and up to about 1000 microns or above.

SUMMARY OF THE INVENTION

[0004] In accordance with the present invention, coherent materials,such as bodies, films, or coatings, are produced by depositing on asubstrate a precursor suspension of finely divided particulates in acarrier fluid. Generally contemporaneous with depositing the precursorsuspension from a first source, hot gases, such as hot gases producedfrom a flame by burning a flammable fluid, is applied to the depositedprecursor suspension from a remote second source to evaporate carrierliquid, such as water or organic solvent if the carrier fluid is aliquid, and to fuse the particulates and thereby form the coherentmaterial The hot gases may carry precursor chemicals or may be derivedfrom a CCVD flame in which precursor chemicals are dissolved in aflammable fluid and reacted by the flame-produced hot gases so as toco-deposit along with the particulates to form a portion of the coherentmaterial. Likewise, the precursor suspension may contain dissolvedmaterial that co-deposits with the particulates to form a portion of thecoherent material and/or a precursor of a material that co-deposits withthe particulates to form a portion of the coherent material.Co-deposited material may be used to effect the properties of thecoherent material. For example, co-deposited material may include curecatalysts and/or cross-linking agents for polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The FIGURE is a diagrammatic illustration of deposition of aspray of precursor suspension onto a substrate and simultaneousapplication of a hot gas-producing flame to the deposited suspension tofuse the particulates and thereby form a coherent material on thesubstrate.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[0006] Illustrated in the FIGURE is apparatus for depositing a coherentmaterial, such as a coating, on the surface of a substrate 10. Aprecursor suspension of particulates in a carrier fluid is atomized by anozzle 12 to produce a spray 14 of the suspension that is directed atthe substrate. Simultaneous with deposition of the sprayed precursorsuspension on the substrate 10, a flame 16 is directed from remotesecond nozzle 18 at the substrate 10 so as to evaporate carrier liquidfrom the deposited precursor fluid and fuse or fuse and cure theprecursor material to thereby form the cohesive material, e.g., thecoating.

[0007] While a flame is the preferred source of hot gases, other methodsof producing a heated gas flow can be used in place of the flame 16.Nozzle 18 could be a heated metal body from which hot gases flow ornozzle 18 could be a plasma source. The gas temperature when interactingwith the spray should be below 2000° C. and preferably below 1000° C.Excessive temperature can result in damage to the substrate or mediumand/or to the material that is being deposited. The key aspect of theflame or heat source 16 and the nozzle 18 is that sufficient energyresults in a gas flow that upon entraining into the suspension spray andflow over the substrate surface provides sufficient bonding, e.g.,binding or sintering, occurs to produce a coherent film or coating or toform a body.

[0008] The nozzle 18 may be a CCVD nozzle, such as those described inthe above-referenced U.S. Pat. Nos. 5,652,021 and 5,997,956, thatproduces a flame from a flammable fluid that contains at least oneprecursor chemical for forming a material that co-deposits on thesubstrate 10 along with the suspension spray 14 from nozzle 12. If theflame 16 is a CCVD flame that co-deposits material, the flame isdirected at the substrate 10 simultaneously with deposition of thesuspension spray 14 from nozzle 12 such that the material deposited bythe CCVD flame is deposited along with the suspension spray 14.

[0009] If the flame 16 is used merely to fuse or fuse and cure, it canbe applied simultaneously to the substrate along with suspension spray14 application, or it can be applied to the area of suspension sprayapplication just subsequent to application of suspension spray 14. Indepositions of this type, to provide uniform coating over the substratesurface, there is typically provided means (not shown) for moving(rastering) the substrate 10 relative to the precursor fluid nozzle 12and flammable fluid nozzle 18. In the FIGURE, the suspension nozzle 12is directed at the substrate 10 at an angle α of approximately 45°;however, this may vary depending upon particular depositionrequirements. For example, if the suspension spray 14 and flame 16 neednot be applied exactly simultaneously, both the suspension spray andflame could be pointed directly at the substrate 10. Variations of theillustrated apparatus may be envisioned. For example, two or more flamenozzles may be disposed in an array around a suspension spray nozzle,particularly when the substrate is rastered relative to the depositionnozzles.

[0010] Another embodiment is that the precursor particulates are in adry powder form suspended in a gaseous fluid and are fed through adirecting device 12, such as an air nozzle or an electrostatic sprayer,yielding a particulate/gas stream 14. This aspect obviates anyevaporation step. Further, if also using a CCVD flame, this allows theCCVD-produced materials to interact with the particulates sooner. It isto be noted that the bulk of the material being deposited is not sentthrough the main energizing environment as is the case with CCVD andthermal spray. These relatively small particulates would be excessivelychanged in morphology or chemistry if exposed to high temperatures.

[0011] One type of atomizer nozzle is the nozzle of a venturi effectsprayer, such as that sold by Kool Mist® sprayer. Precursor fluids canalso be atomized, as is done in conventional CCVD atomization, byforcing the precursor fluid under pressure through a constricted nozzleor needle. Such is described, for example, in above-referenced U.S. Pat.No. 5,997,956.

[0012] An important utility of the present invention is to produce oxidefilms formed, at least in part, from oxide particulates, such as silicaparticulates. An oxide particulate suspension comprises an aqueousmedium in which is suspended between about 0.1 and about 10 wt % oxideparticulates, preferably between about 0.5 and about 5 wt % oxideparticulates. The suspension must not be too concentrated or it may betoo viscous to flow easily through supply lines or in the atomizer. Itshould not be too dilute, or deposition times will be excessive andenergy use to evaporate carrier liquid will be excessive. Generally, itis preferred to use as concentrated a suspension as is consistent withease of application, including ease of atomization.

[0013] In general, any inorganic particulates may be deposited. Suitableoxide particulates for use in the invention include, but are not limitedto silica, alumina, alumina silicates, ceria, yttria, magnesia, titania,glasses, and mixtures thereof. Metals that may be deposited include, butare not limited to, platinum, gold, silver, nickel, copper, chromium andmixtures thereof. Metals, metalloids, nitrides, carbides, borides,phosphates, carbonates, borates, mixtures thereof, etc., may bedeposited as particulates, either as liquid suspensions or asgas-entrained dry powders.

[0014] Generally the particulate suspension, e.g., of oxideparticulates, is aqueous, but it is contemplated that the suspension maycomprise organic components, including solvents, suspension promoters,surfactants, etc., that are consistent with the requirements of filmformation and consistent with the desired end properties of the coating.Typically, such organic components comprise up to about 30 wt % of thesuspension. To this end, it is preferred that any organic component(s)either evaporate or burn away leaving no deposit upon application of thehot gases or else leave a residue that is at least consistent with thedesired use of the coating or which may possibly impart beneficialcharacteristics to the coating. As an example of imparting desiredproperties, an alkali metal-containing surfactant, such as sodiumlaurate, may be used to promote suspension of particulates if the alkalimetal oxide that will be co-deposited with the particulates is desiredfor altering the microstructure or electrical, e.g., dielectric,characteristics of a deposited film. Organic components may also act asbinding agents for the particulates.

[0015] The particulates, e.g., oxide particulates, themselves may rangein average particulate size (as measured along the greatest dimension ofthe particulate) of between about 0.001 micron to about 10 microns,preferably between about 0.01 to about 2 microns. The size of theinitial particulates may be expected to affect properties of the coatingthat is formed, although this aspect has not been fully explored. Theparticulates need not be identical in chemical composition, and amixture of two or more types of particulates may be suspended. However,the two types of particulates must be capable of being joined into acoherent material by co-sintering, by co-deposition using a CCVD flame,or by binding agents that are contained in or produced from either theparticulate suspension or the hot gas stream.

[0016] Certain commercial formulations are useful for use as the oxideparticulate-containing deposition. For example, Beuhler® silica containsbetween about 30 and about 60 wt % silica particulates of averageparticulate size of 0.06 microns. Such a concentrated solution istypically diluted to facilitate atomization.

[0017] The particulate suspension, in addition to the particulates, maycontain additional components that may be incorporated into the film orwhich may, upon treatment, e.g. combustion or exposure to hot gases,produce materials that are incorporated, along with the particulates,into the coherent material that forms.

[0018] The flammable fluid that burns to form the hot gas-producingflame is an organic fuel or mixture of organic fuels that may or may notcontain precursors, e.g., dissolved or suspended precursors, formaterials that are to be co-deposited with the particulates. The flamemay be simply formed from a gaseous (at standard temperature andpressure) hydrocarbon, such as propane or butane, or from a liquidhydrocarbon, such as toluene. For many applications in which the flameco-deposits a desired material, the fuel is a mixture of hydrocarbons,such as a mixture of propane and toluene.

[0019] Hot gas temperature must be sufficient to bind or sinter theparticulates from the precursor suspension. For sintering silicaparticulates, gas temperatures entrained into the particulate-containingspray are typically 800 to 1000° C. Flame or entrained gas temperatureswill vary, depending upon the particulate material and/or organicmaterial to be sintered or bound.

[0020] When depositing a suspension of particulates, a CCVD depositionof a material(s), that is the same or different from the particulates,may be used. For example, when the particulate material is silica, aCCVD solution containing a silica precursor, such as tetraethoxysilane(TEOS) or tetramethylsilane (TMS), may be used to co-depositflame-produced silica that helps bind the particulates together. Othermaterials, particularly yttria and sodium, may serve as adhesionpromoters between particulates. Yttria may be deposited by the CCVDflame or may be formed when the CCVD flame burns an yttrium-containingprecursor chemical co-deposited with the particulates from thesuspension. Oxides which are conveniently deposited by CCVD flameinclude, but are not limited to, silica, yttria, ceria, chromia,alumina, alumina silicates, glasses, and mixtures of such oxides. A widevariety of precursors may be added to the solution that forms the CCVDflame which impart a variety of properties to the film. Precursors fordepositing materials containing a variety of chemical elements include,but are not limited to:

[0021] Ag silver nitrate, silver trifluoroacetate, silver acetate,silver cyclohexanebutyrate, silver 2-ethylhexanoate

[0022] Al aluminum nitrate nonahydrate, aluminum acetylacetonate,triethylaluminum, aluminum sec-butoxide, aluminum iso-propoxide,aluminum bis(2-ethylhexanoate)monohydroxide

[0023] Au chlorotriethylphosphine gold (I), chlorotriphenylphosphinegold (I)

[0024] B trimethylborate, trimethoxyboroxine

[0025] Ba barium 2-ethylhexanoate, barium nitrate, bariumacetylacetonate hydrate,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)barium hydrate

[0026] Bi bismuth (III) nitrate pentahydrate, bismuth (III)2-ethylhexonate

[0027] Cd cadmium nitrate tetrahydrate, cadmium 2-ethylhexanoate

[0028] Ce cerium (III) 2-ethylhexanoate

[0029] Cr chromium (III) nitrate nonahydrate, chromium (III)2-ethylhexanoate, chromium (III) sulfate hydrate, chromium hexacarbonyl,chromium (III) acetylacetonate

[0030] Cu copper (II) 2-ethylhexanoate, copper (II) nitrate trihydrate,copper (II) acetylacetonate hydrate

[0031] Co cobalt naphthenate, dicobalt octacarbonyl, cobalt (II) nitratehexahydrate

[0032] Fe iron (III) nitrate nonahydrate, iron (III) acetylacetonate

[0033] In indium (III) nitrate hydrate, indium (III) acetylacetonate

[0034] Ir dihydrogen hexachloroiridate (IV) hydrate, iridium (III)acetylacetonate, dodecacarbonyltetrairidium

[0035] K potassium ethoxide, potassium tert-butoxide,2,2,6,6-tetramethylheptane-3,5-dionato potassium

[0036] La lanthanum (III) 2-ethylhexanoate, lanthanum (III) nitratehexahydrate, lanthanum (III) acetylacetonate hydrate, lanthanum (III)iso-propoxide, tris(2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum(III)

[0037] Li 2,2,6,6-tetramethylheptane-3,5-dionato lithium, lithiumethoxide lithium tert-butoxide

[0038] Mg magnesium naphthenate, magnesium 2-ethylhexanoate,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)magnesium dihydrate,magnesium acetylacetonate, magnesium nitrate hexahydrate

[0039] Mo ammonium molybdate tetrahydrate, molybdenum hexacarbonyl,molybdenum (IV) dioxide bis(acetylacetonate)

[0040] Na 2,2,6,6-tetramethylheptane-3,5-dionato sodium, sodiumethoxide, sodium tert-butoxide

[0041] Nb niobium (V) ethoxide,tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato) niobium (VI), niobium(IV) (2-ethylhexanoate)

[0042] Ni nickel (II) nitrate hexahydrate, nickel (II) acetylacetonate,nickel (II) 2-ethylhexanoate, nickel (II) napthenate, nickel carbonyl

[0043] P triethylphosphate, triethylphosphite, triphenylphosphite

[0044] Pb lead (II) 2-ethylhexanoate, lead naphthenate,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)lead (II), lead (II) nitrate

[0045] Pd diamminepalladium (II) nitrite, palladium (II)acetylacetonate, ammonium hexochloropalladate (IV)

[0046] Pt platinum (II) acetylacetonate, platinum (II)hexafluoroacetylacetonate, diphenyl(1,5-cyclooctadiene)platinum (II),diammineplatinum (II) nitrite, tetraammineplatinum (II) nitrate

[0047] Ru ruthenium (III) acetylacetonate

[0048] Si tetraethoxysilane, tetramethylsilane, disilicic acid,metasilicic acid

[0049] Sn tin (II) chloride dihydrate, tin (II) 2-ethylhexanoate,tetra-n-butyltin, tetramethyltin

[0050] Sr strontium nitrate, strontium 2-ethylhexanoate,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)strontium hydrate

[0051] Ti titanium (IV) iso-propoxide, titanium (IV) acetylacetonate,titanium (di-isopropoxide)bis(acetylacetonate), titanium (IV)n-butoxide, titanium (IV) 2-ethylhexoxide, titanium (IV) oxidebis(acetylacetonate)

[0052] W tungsten hexacarbonyl, tungsten (VI) fluoride, tungstic acid

[0053] Y yttrium (III) 2-ethylhexanoate, yttrium (III) nitratehexahydrate, yttrium (III) iso-propoxide, yttrium (III) napthoate

[0054] Yb ytterbium (III) nitrate pentahydrate

[0055] Zn zinc 2-ethylhexanoate, zinc nitrate hexahydrate, zinc acetate

[0056] Zr zirconium (IV) 2-ethylhexanoate, zirconium (IV) n-butoxide,zirconium (IV) hexafluoroacetylacetonate, zirconium (IV)acetylacetonate, zirconium (IV) n-propoxide, zirconium dinitrate oxide

[0057] In coherent material produced in accordance with the invention,about 1 wt % to 100% of the coherent material will derive fromparticulates, and 0 to about 99 wt % from non-particulate chemicals inthe precursor fluid and/or a flammible fluid. Preferably about 50 wt %to about 99 wt % of the material will derive from particulates, andbetween about 1 wt % to about 50 wt % of the material is derived fromnon-particulate chemicals in the precursor fluid and/or a flammiblefluid.

[0058] While an important use of the method of the present invention isin depositing oxide-based materials, other materials can also beproduced from deposition of a particulate suspension spray on asubstrate along with generally contemporaneous application of a flame orhot gases to the deposited suspension spray.

[0059] As the suspension, finely divided metal particulates may besuspended in water or an aqueous solution. A flame is generallycontemporaneously applied to the deposited suspension to evaporate waterand fuse the metal particulates. Gas temperature depends upon thebinding or sintering temperature of the metal or of any incorporatedbinding components. If oxide-free metals are desired, the process of thepresent invention is most useful for depositing metals with low oxygensusceptibility, such as gold, silver, platinum, and mixtures thereof,although other oxide-free metals may be deposited if a reducing flame isused. Useful particulate size is similar to particulate size mentionedabove with respect to oxide particulates, with the understanding thatmetals are often more dense than oxides requiring smaller particulatesizes for the particulates to be maintained as stable suspensions.Likewise, concentrations of suspended metal particulates are similar tooxide particulate concentrations mentioned above.

[0060] The suspending fluid of the particulate suspension may be a gasin which particulates are suspended and carried to the substrate.

[0061] Again with metals, the flame may be used only for the purpose ofproviding energy to evaporate the carrier fluid and evaporating thesolvent. Or the flame may contain precursor chemicals for co-depositingwith the metal particulates. For example, when finely divided platinumparticulates are deposited in the precursor flame, the solution that isburned to form the flame may contain a platinum precursor, such asplatinum acetylacetonate, that co-deposits platinum and helps to fusethe platinum particulates together. Or when depositing a suspension ofplatinum particulates, the CCVD flame may contain an oxide precursor,such as a silica precursor. The co-deposited oxide increases theelectrical resistivity of the fused platinum coating that forms, makingthe material suitable for forming thin film, embedded resistors.Co-deposition of polymeric materials and clay (alumina silicates) mayproduce a gas-barrier coating.

[0062] Polymeric coatings may be similarly formed from a suspension thatcomprises suspended polymeric material along with generallycontemporaneous application of a flame to the deposited precursorsuspension. To be suitable for application by this method, the polymermust be fusible by hot gases, e.g., flame-produced hot gases, applied ata certain temperature range without the hot gases degrading the polymer.Some particularly useful flame-resistant polymers that may be applied asparticulate suspensions by the method of the present invention includepolyimide, polyamide/imide and polytetrafluoroethylene. Polyimide and/orpolyamide/imide may be formed from dissolved or suspended polyamicacids. Particulate size and concentrations of polymer particulates maybe similar to those discussed above with respect to oxide particulatesand metal particulates, although because polymers are typically lessdense than either oxides or metals, suspension of larger polymerparticulates may form stable suspensions and thus be useful in theprocess of the invention.

[0063] If a polymer is water-soluble, the polymer may be dissolved in anaqueous precursor suspension of particulates of similar or differentmaterials. Likewise, solvent-soluble polymers may be dissolved in anorganic precursor suspension of particulates of similar or differentmaterials. The concentration of dissolved polymers used may depend uponthe viscosity of the solution, which must be consistent with ease ofspray application.

[0064] Suspended polymer particulates may be a thermoplastic, in whichcase the hot gases are applied to the deposited spray to evaporatecarrier liquid and fuse the thermoplastic polymer. If the suspendedpolymer is a thermosetting composition, the flame may both fuse and curethe polymer. In the case of a thermosetting polymer, either the carrierfluid of the suspension and/or a flammable fluid that produces a hotgas-producing flame may provide a cross-linking agent and/or a curecatalyst for the thermosetting polymer.

[0065] The carrier fluid used to form the precursor suspension inaccordance with the present invention is generally water or an aqueoussolution. The carrier fluid may be an organic solvent. However, in viewof the fact that a flame is applied, careful selection of any suchsolvent must be made to ensure that its vapor pressure and combustiontemperature are consistent with safety.

[0066] The method of the invention is suitable for deposition on a widevariety of substrates, including but not limited to metals, ceramics(including glass), polymeric materials, material composites, etc. Inaddition to utilitarian applications of the invention stated above,decorative coatings may be applied as well. The formed material may behomogenous or may vary in composition, material, size, porosity,permeability, and thus yield gradient and/or layered structuresvertically and/or laterally.

[0067] The present invention may also be used to form a body ofmaterials that may or may not contain the original substrate or mediumon which the material formed. The sprays may be directed, channeled, ormasked, such that a desired shape or pattern is formed. The substratemay have a low adhesion to the formed coherent material, or thesubstrate may be removed by chemical processing. The formed material mayalso be an enlarged particulate formed in the gas stream and collectedvia powder and particulate gathering methods. The formed material may bea continuous or a patterned film.

[0068] The invention will now be described in greater detail by way ofspecific Examples.

Example 1

[0069] An aqueous suspension of extremely small particulate size silica(0.06 μm Beuhler® SiO₂ polishing compound) was diluted to a 2.5% weightsolution in de-ionized water and sprayed onto the substrate in advanceof a CCVD flame carrying silica produced from TEOS (2.1% Si in isopropylalcohol as precursor). The Beuhler suspension was atomized through aKool Mist®, sprayer that operates by venturi effect. Kool Mist® sprayeris commonly used in machine tools for misting machined parts withcooling oil. The HPLC pump rate to the CCVD flame was 4.00 ml/min at aVariac® setting of 2.50 amperes, and tip O₂ flow rate of 3.8 L/min.

[0070] The CCVD flame head was positioned precisely five incheslaterally from the suspension spray head, equidistant to the substrate,and at a 45° angle normal to the substrate surface (FIG. 1). Thisgeometry placed the sample surface just beyond the end of the visibleportion of the flame, resulting in a gas temperature at the substratesurface of ˜800-900° C., although this was difficult to measureaccurately.

[0071] In the present case, the substrate was stationary while the KoolMist® Sprayer and the atomizer moved to produce the silica coating. Amotion program was employed to coat the substrate at 25 inches perminute. A total of sixty passes were conducted to produce the coating in50 minutes. As a means of preheating the substrate, a TEOS flame wasapplied for 5 minutes. It is ideal, due to the nature of the Al—SiCcomposite that the flame does not dwell on the substrate. To ensure ofproper curing of the precursor upon substrate, the final fifteen minutesof deposition was purely the CCVD TEOS flame.

Example 2

[0072] The following solutions were prepared:

[0073] Yttrium stock solution: 0.7 wt % yttrium as yttrium2-ethylhexanoate (Yt-EH) in toluene.

[0074] Solution A: 5 ml Beuhler® silica suspension mixed with 135 ml.H₂O.

[0075] Solution B: 0.3 g Yttrium stock solution mixed with 25 ml. H₂O.

[0076] Deposition solution: 1:1 mixture of Solutions A and B by volume.

[0077] The flame in this example was produced from 100%o propane.

[0078] Films were deposited generally under the conditions of Example 1.The Yt-EH is oxidized by the flame to produce yttria which acts as anadhesion promoter in the deposited film.

Example 3

[0079] A flammable solution for depositing ceria from a CCVD flame isformed from a stock solution that is 1.8% by weight of cerium of cerium2-ethylhexanoate in toluene. The stock solution is then dissolved in 48ml toluene and 204 g. propane.

[0080] Several advantages of the invention over other deposition methodsshould be appreciated. An advantage of this co-deposition process versusthermal spray is the materials here are not subjected directly to thehigh heat zone of a plasma which would cause many materials, especiallysmall grain materials, to be evaporated. The co-deposition processallows such materials to stay as small particulates and have thedifferent materials then maintain more of a size close to their originalsize. Also, a number of materials subjected to a plasma sprayenvironment are decomposed or altered excessively. The present inventionenables materials such as polymers, very fine grains, silicas, etc. tobe deposited without excessively altering the properties or decomposingthe materials. The materials are able to be broken up and sprayed at asurface prior to being subjected to the heat. The heat is more focusedat the surface and not at the spray itself but usually in the area ofwhere the spray intercepts the surface so the particles are only heatedslightly prior to meeting the surface. If the heat source, i.e., heatedgases, were too distal from the spray impact area, if a liquid spraywere used, then the materials might drip and run. By having the hotgases present right at the surface of the spray, the liquid is able tobe evaporated. If a powder is being deposited, the powder is able tosinter and form onto the surface rather than being blown off thesurface. So it is enabled for the powder to be a little sticky if itwere a dry powder feed versus the wet.

[0081] These aspects significantly differentiate the present inventionfrom thermal spray or processes where a substrate is sprayed and thenheated afterwards to cause the coating to densify with the advantages ofno dripping occuring and more material sticking to the surface.

[0082] The co-deposition process is also significantly different fromspray pyrolysis where the substrate is heated to a higher point whereinmany substrates cannot handle the correct heat amount required to causethe coating to become coherent. It is difficult to heat a subject, inparticular a coating, in certain areas of a larger substrate.

[0083] The particles that are co-deposited can be man-made or groundpowders or of natural materials of natural size. Potentially materialsfrom nature include clays, brown cords (?), micas and other materialsthat can be aligned in certain structures for increased strength or gasdiffusion barrier type properties. Plate-like materials when depositedby the present invention can form a preferred orientation, e.g., layingdown with the plate surfaces normal to the flame aligning with thesurface of the substrate. Clays in general are luminous oriented.

What is claimed:
 1. A method of forming a coherent material on a substrate comprising: providing a precursor suspension of particulates in a carrier fluid, from a first source, directing said precursor suspension at a surface of said substrate to deposit said precursor suspension on said substrate surface, and generally contemporaneously with depositing said precursor suspension on said substrate surface, from a second source that is displaced relative to said first source, directing hot gases at said deposited precursor suspension to fuse said particulates into the coherent material.
 2. The method according to claim 1 wherein said hot gases from said second source comprise a material or a precursor of a material that co-deposits on said substrate with said particulates.
 3. The method according to claim 1 wherein a flammible fluid is combusted at said second source to form said hot gases.
 4. The method according to claim 3 wherein said flame is produced from a flammable fluid comprising at least one organic fuel and at least one precursor chemical that produces a material that co-deposits with said precursor suspension on said substrate.
 5. The method according to claim 1 wherein said precursor suspension further comprises at least one precursor chemical that produces a material upon exposure to said hot gases, which along with said fused particulates, forms a portion of said coherent material
 6. The method according to claim 1 wherein said precursor suspension contains a material or a precursor of a material that forms, along with said particulates, a portion of said coherent material, and/or said hot gases carry a material or a precursor of a material that forms, along with said particulates, a portion of said coherent material.
 7. The method according to claim 1 wherein between about 50 wt % and about 99 wt % of said coherent material is derived from said particulates of said suspension, and between about 1 and about 50 wt % comprises material derived from non-particulate chemicals contained in said precursor suspension and/or carried by said hot gases.
 8. The method according to claim 1 wherein said particulates comprises oxide particulates.
 9. The method according to claim 1 wherein said particulates comprise particulates comprise materials selected from the group consisting of silica, alumina, alumina silicates, ceria, yttria, magnesia, titania, glasses, and mixtures thereof.
 10. The method according to claim 1 wherein said precursor suspension comprises an oxide precursor and/or said hot gases carry an oxide precursor.
 11. The method according to claim 1 wherein said method is used to produce a coherent material between about 10 and about 1000 microns or greater in thickness.
 12. The method according to claim 1 wherein said method is used to produce a coherent material layer at least about 1 microns in thickness.
 13. The method according to claim 1 wherein said method is used to produce a coherent material at least about 10 microns in thickness.
 14. The method according to claim 1 wherein said method is used to produce a coherent material at least about 20 microns in thickness.
 15. The method according to claim 1 wherein said particulates comprise metal particulates.
 16. The method according to claim 15 wherein said precursor suspension and/or said hot gases comprises an oxide-producing precursor.
 17. The method according to claim 1 wherein said precursor suspension and/or said hot gases comprises a metal-producing precursor.
 18. The method according to claim 1 wherein said particulates comprise a metal selected from the group consisting of gold, silver, platinum, nickel, copper, chromium, and mixtures thereof.
 19. The method according to claim 1 wherein said precursor suspension and/or said hot gases comprises an oxide-producing precursor.
 20. The method according to claim 1 wherein said carrier liquid comprises water.
 21. The method according to claim 1 wherein said particulates comprise a polymeric material.
 22. The method according to claim 1 wherein said precursor suspension further comprises polymeric material dissolved in said carrier liquid.
 23. The method according to claim 1 wherein said precursor suspension further comprises a material selected from the group consisting of polyimide, polyamide/imide and polyamic acid.
 24. The method according to claim 1 wherein said precursor suspension comprises a thermosetting polymer and said precursor fluid and/or said hot gases comprises a chemical selected from the group consisting of a crosslinking agent for said thermosetting polymer, a cure catalyst for said thermosetting polymer, or a mixture thereof.
 25. The method according to claim 1 wherein the average particle size of particulates in said suspension range from 0.001 to 10 microns.
 26. The method according to claim 1 wherein the average particle size of particulates in said suspension range from 0.01 to 20 microns. 